43 
More precise determination of the potency of serums injected into 
mice which remain entirely well after the injection of 0.4 c. c. of the 
mixture is made by firrther experiments. If m tliis way we obtain 
the L° value of the serum, we are enabled by a simple process of 
calculation to determine the antitoxic worth of the sermn. That 
quantity of sermn m 0.4 c. c. of the mixture containing 0.01 c. c. of 
test poison Xo. 5 ( = L® dose) contains exactly yoVcr of an immunity 
unit. 
Behring’s notations, generally used in the German literature, are as 
follows : 
1+Ms represents the fatal dose for 1 gram of mouse. 
1+M represents the fatal dose for 1 gi-am of guinea pig. 
Ms’^ represents 15 times the minimal lethal dose for 1 gi-am of mouse. 
The toxine is always represented by the plus sign, the antitoxin by the minus sign. 
The present modification of the methods for testing tetanus anti- 
toxin at Elmlich’s institute are largely based upon the work of Marxy 
who found that the tetanus toxine could be preserved in a stable con- 
dition in a dried state in Elrrlich vacuum tubes. 
The official testing of antitoxin is carried out in the following man- 
ner: One of the vacuum tubes containing the poison and another con- 
taining the serum are carefully opened by means of a file, and a cer- 
tain quantity of water, say 5 c. c., added to each tube from a gradu- 
ated pipette. The tubes are then carefidly closed vdth a bimit cork. 
Each tube — the one containing toxine and the other serum — is now 
shaken many times in order to insure the complete solution of its 
contents. The contents of each tube are next emptied and carefidly 
washed out vdth the remaining quantity of the diluting fluid. The 
serum must be so diluted that 1 c. c. of the solution represents just 
0.01 of an immunity unit. After tliis has been accomplished the 
mixture of the toxine and antitoxin in vitro is made. For this pur- 
pose two series of eight flasks each are necessary. One c. c. of the 
standard serum solution is placed in each flask of the first series; 1 
,c. c. of a dilution of the unknown serum to be tested is placed in each 
flask o.f the second series. To each series is now added the folloiving 
test doses of toxine, varidng in accordance with the toxine from 0.8 
to 1.5 c. c. These doses are so calculated that all the values from L® 
E.; Mitteilungen aus der pmlimgstechnischen Praxis. Festschi'ift f. Eo 
bert Koch. Jena, Gustav Fischer, 1903. 
; Diagnostik, Serumtherapie imd Prophylaxe. Bibliothek t. Coler, vol. 11, 
Berlin, 1902. 
Bonitz. tv.: Die tVertbemessung der Schutz- und Heilsera. Handbuch Kolle-tVas- 
sermann. vol. 4, part 2. 
